Preparation And Properties Of High Thermal Conductivity Insulation Silicone Composites

With the development of high integration and high power density of electronic components,the heat dissipation has an influence to the use efficiency and stability of electronic devices.In addition,the electromagnetic interference problems caused by high-frequency circuits between highly integrated electronic components are becoming more and more serious.Therefore,it is very significant to develop a kind of new thermal conductive potting composite materials with high thermal conductivity and electromagnetic shielding.In this work,by using compounding and surface modification methods,the potting composite materials with high thermal conductivity,electrical insulation and certain electromagnetic shielding properties are prepared.The main research results are as follows:The single particle size filler can not form enough heat conduction paths,in order to form a sufficient number of heat conduction paths,a compounding method was used.Spherical Al₂O₃ with a particle size of 2?m and 5?m were compounded with 40?m spherical Al2O3,30?m spherical AlN,55?m spherical AlN and 80?m spherical AlN,respectivity.Finally,potting composites were prepared.The thermal conductivity increases with the particle size of the fillers,reaching a maximum of 2.14 W·m^-1K^-1.The volume resistivity are at 10¹⁴?·cm.The dielectric constant is between 1.2 and 3.4,dielectric loss is between 0.001 and 0.02.The electromagnetic shielding effective is between 74.88%and 31.92%.The viscosity of each component before curing is kept below 35000 mP·s.The linear expansion coefficient is less than 10^-5 K^-1.The thermal decomposition temperature of the composite materials is 260°C.The interface thermal resistance is an important factor affecting the thermal conductivity of composite materials,in order to reduce the interface thermal resistance between the substrate and the filler,compounding and surface modification methods were used.Spherical Al2O3 of 2?m and 5?m were compounded with 80?m spherical AlN.The surface of fillers were modified with different amounts of octavinyl-POSS.Finally,potting composites were prepared.The thermal conductivity first increases first and then decreases as the amount of added modifier increases,and reaches a maximum of 2.36 W·m^-1K^-1 at an added amount of 0.3 wt%.The volume resistivities are at 10¹⁴?·cm.The dielectric constant is between 2.3 and 2.9,the dielectric loss is between0.002 and 0.02.The electromagnetic shielding effective is between 71.58%and 34.23%.The viscosity of each component before curing is kept below 35000 mP·s.The linear expansion coefficient is less than 10^-5 K^-1.The thermal decomposition temperature of the composite materials is 260°C.In order to further improve the thermal conductivity and electromagnetic shielding rate of composite materials,compounding and surface modification methods were used.Spherical Al₂O₃ of 2?m and 5?m were compounded with 80?m spherical AlN.The surface of the fillers were modified with 0.3 wt%octavinyl-POSS modifier.Meanwhile,the CuFeO₂@PDA nanoparticles coated with polydopamine on the surface were also used as thermal conductive fillers.The thermal conductivity reaches 2.82 W·m^-1K^-1.The volume resistivity is at 7.04×10¹³?·cm.The dielectric constant is between 4 and4.5,the dielectric loss are around 0.02.The electromagnetic shielding effective is between 78.96%and 32.55%.The viscosity of each component before curing is kept below 35000 mP·s.The linear expansion coefficient is less than 10^-5 K^-1.The thermal decomposition temperature of the composite materials is 280°C.